Why is carbon 126 and carbon 146 a pair of isotopes

Answer 1

Carbon-12 and carbon-14 are a pair of isotopes because they both have the same number of protons in their nuclei (6), but different numbers of neutrons. Carbon-12 has 6 neutrons and carbon-14 has 8 neutrons. This difference in neutron number results in different atomic weights for each isotope, but they still have the same number of protons and therefore have similar chemical properties.